Blair, born in Southfield, Michigan , emerged from a background in legal and political involvement: both her parents were lawyers and her father active in the U.
Democratic Party. Blair's upbringing was predominantly Jewish. She initially pursued photography at Kalamazoo College before moving to New York to become involved in the arts, graduating from the University of Michigan. Blair's early career was marked by numerous auditions to land her first roles in television and film, with her breakthrough in Cruel Intentions and subsequent mainstream success in projects like Legally Blonde and Hellboy.
Blair's personal life include her marriage to Ahmet Zappa and subsequent relationships and motherhood. After being diagnosed with multiple sclerosis MS in , she has shared her experience with the condition, contributing to her advocacy work. Her maternal grandfather was the founder of Penn Fruit and she spent a great deal of her childhood in Philadelphia. Democratic Party until his death in ; her mother died in Her parents divorced when Blair was Selma and her sister Elizabeth officially changed their surname to 'Blair'; in her memoir, Blair wrote that, following a concerted effort on the part of her father's girlfriend to derail her career, she did not speak to her father for 12 years.
Blair's father and maternal grandfather were Jewish; her Scottish maternal grandmother, and her mother, were Anglican but Selma and her sisters had a Jewish upbringing and Selma formally converted to Judaism in the second grade; her Hebrew name is 'Bat-Sheva'. She then spent two years β studying photography at Kalamazoo College. She returned to Michigan, transferred from NYU to the University of Michigan and, in , graduated magna cum laude with a triple major in photography, psychology, and English.
She then returned to New York City to pursue a career in the arts. In , during her time at Cranbrook Kingswood, Blair was involved in a production of T. She considered it a failure, but her English teacher told her not to give up; that was the first time she thought she could be an actress.
